1. Field of the Invention
The present invention relates to a source driver of a Liquid Crystal Display (LCD), and more particularly, to a source driver of an LCD for black insertion technology.
2. Description of the Prior Art
The LCD utilizes the spinning of liquid crystal particles to control luminance of the light passing through for displaying different grey levels. Compared to the impulse-type of the Cathode Ray Tube (CRT), the LCD utilizes hold-type. However, since the liquid crystal particles spin continuously, the response time of the LCD is longer than the CRT, which causes worse performance on motion pictures than CRT and therefore generates motion blur. In order to solve motion blur, the LCD inserts black frames between displaying frames for simulating impulse-type of the CRT. The manner for inserting black frames may be, for example, turning on/off the backlight module for inserting black frames, or utilizing the drive circuits to insert black frames.
Please refer to FIG. 1, which is a diagram illustrating data transmission of a conventional LCD. When the LCD uses black frame insertion for writing data, the display data and the black data have to be written interlacingly, which increases the frame rate. As shown in FIG. 1, successive to the (n+2)th and the (n+3)th frames, two black frames are inserted respectively. In this way, when the LCD utilizes black frame insertion, six frames have to be displayed within four frame periods. That is, the frame rate is increased to be 1.5 times the original frame rate.
Please refer to FIG. 2 and FIG. 3. FIG. 2 is a timing diagram illustrating the signals of the source driver. FIG. 3 is a timing diagram illustrating the signals when the source driver writes black data. STH represents the start signal, DATA represents the display data, TP represents the load signal, Tc represents the minimal charging time, and Td1 and Td2 represent the writing time of the display data. As shown in FIG. 2, the source driver outputs the display data DATA to the display panel at the moment A, and the display panel finishes charging at the moment B. As shown in FIG. 3, when the source driver writes the black data, the writing time of the display data DATA is reduced from Td1 to Td2. Even though the charging time Tc falls still within the minimal allowable range, the writing time Td2 possibly reaches the up limit of the capability of the source driver. When the writing time of the display data is reduced, the frame rate is increased. By doing so, when the LCD with great size utilizes the black frame insertion, some problems, e.g. Electromagnetic Interference (EMI), or signal attenuation, may occur. Thus, the writing time of the black data has to be reduced to avoid greatly increasing the frame rate of the LCD.